A novel synthesis of (E)-gem-dimetalloalkenes containing boron and silicon:: An easy access to alkyl trimethylsilyl ketones

A simple, novel synthesis of (E)-gem-dimetalloalkenes containing boron and silicon based on (Z)-1-bromo-1-alkenylboronate esters is developed. 1-Bromo-(Z)-1-alkenylboronate esters readily available from literature procedures smoothly undergo a reaction with trimethylsilyllithium (easily generated from hexamethyldisilane with methyllithium in hexamethylphosphoramide) to provide the corresponding 'ate' complexes. These 'ate' complexes undergo intramolecular nucleophilic substitution reaction to provide the corresponding (E)-1-alkenylboronate esters containing trimethylsilyl moiety in good isolated yields (72-85%). The carbon skeletons present in these intermediates are confirmed by oxidation to the corresponding alkyl trimethylsilyl ketones with sodium acetate and hydrogen peroxide.